The present invention relates to high resolution digital imaging and in particular to a digital x-ray imaging system and method utilizing a single digital camera.
In conventional x-ray imaging a photographic film is exposed to visible light produced by a fluorescent imaging screen in response to x-ray energy which has passed through an object, in order to capture the image of the object being x-rayed. The x-rays are passed through the object and impinge on the fluorescent imaging screen, such as a phosphor imaging screen. The phosphor imaging screen converts some of the radiation into a selected spectral component (typically visible light). The exposure of the photographic film to the spectral component from the phosphor imaging screen produces the image of the object on the photographic film.
Recent advances in x-ray imaging however have resulted in filmless x-ray methods and apparatus. Such a system is disclosed in U.S. Pat. No. 5,309,496, entitled xe2x80x9cFILMLESS X-RAY APPARATUS AND METHOD OF USING THE SAMExe2x80x9d, issued to Winsor, which is hereby incorporated herein by reference. In the preferred embodiment of Winsor, a video camera and a frame grabber are used to provide still x-ray images.
However, in x-ray imaging it is desirable to get very high resolution images so that a health care provider could accurately diagnose a patient. The use of photographic films as used in conventional x-ray imaging systems provides a high degree of resolution desirable in x-ray radiography. However, the video camera and frame grabber of Winsor may not provide the desired high degree of resolution because in the preferred embodiment video camera and frame grabber implementation of Winsor, an image in analog format is filmed by the video camera and a frame grabber used to capture one or more frames. The captured frames may then be digitized. Because of the capture of the image in analog format and the subsequent conversion of the image from analog format to digital format, the desired degree of resolution may not be obtained. Also, as the video tube of the video camera has a fixed life span, it deteriorates over time and accordingly the quality of the image deteriorates over time, which may be evidenced for example by a decrease in the contrast of the image.
Furthermore, in any imaging system, because of the curvature of the lens (or lens assembly), more light passes through the center of the lens than through the edges. Therefore, the intensity of the pixels in the center is greater than the intensity of the pixels at the edges. Because of limitations of the video camera and frame grabber of the preferred embodiment of Winsor, the pixel contrast and/or intensities cannot be modified on an individual basis and therefore, in the final x-ray image the pixels at the center are brighter than those at the edges.
An alternative structure for capturing images is the use of multiple CCD (charge coupled device) cameras. The use of multiple digital cameras is known in other fields. In such applications, different cameras are used to capture different portions of the entire image thereby providing multiple images, which are later merged together in order to create a single image. However, in such applications, a known reference point is added to the original image itself. The different images are merged together using the known reference point. By utilizing the known reference point in the merging process, the combining of the images may be accomplished more efficiently. This procedure, however, adds unwanted artifacts (the reference point itself) to the image. The presence of artifacts in the combined image would be specially undesirable in an x-ray imaging system because of the degree of accuracy preferred in rendering a correct diagnosis of the patient based on the x-rays.
Moreover, in systems that use multiple CCD cameras, it is desirable that the multiple cameras be properly aligned with the object or imaging screen to be photographed. Because of the number of cameras involved in a multiple camera system this process may be quite cumbersome and time consuming. Additionally, proper alignment of the lens, mirror or prism with respect to the object plane, is also desirable. The process of alignment and calibration is very cumbersome and time consuming.
Furthermore, it is desirable to keep the brightness of the different portions of the image consistent especially with varying degrees of light intensity. Accordingly, there are several disadvantages of using multiple digital cameras, although the use of such multiple digital cameras has its associated advantages, such as higher resolution of the image.
Therefore, there is a need in the art for a system and method for rendering high resolution digital x-ray images of an object without the use of multiple cameras.
These and other objects, features and technical advantages are achieved by an x-ray imaging system and method which utilizes a single imaging sensor to acquire an image from an imaging screen.
In a preferred embodiment, the x-ray imaging system comprises a single imaging sensor, such as a digital CCD camera. The digital camera preferably acquires the image from an imaging screen, such as for example, a fluorescent phosphor screen used in x-ray imaging. The digital camera is positioned so that the field of view of the digital camera substantially covers the imaging screen. Light from the imaging screen falls on a redirecting element which redirects the light from the imaging screen onto a lens assembly of the imaging sensor. The elements of the lens assembly focus the image of the object onto a CCD chip which is preferably part of the imaging sensor.
In the preferred embodiment, the imaging apparatus also includes a host processor based system comprising a camera interface for receiving and processing the image from the camera. Such a host processor based system may be for example, a general purpose computer. A preferred embodiment host processor based system is described in the above referenced U.S. patent application entitled xe2x80x9cDIGITAL HIGH RESOLUTION X-RAY IMAGINGxe2x80x9d, which is hereby incorporated herein by reference.
Accordingly, it is a technical advantage of a preferred embodiment of the present invention to provide a high resolution digital x-ray imaging system.
It is another technical advantage of a preferred embodiment of the present invention to provide a seamless x-ray image.
It is still another technical advantage of a preferred embodiment of the present invention to provide high resolution x-ray images without any undesirable image artifacts.
It is still another technical advantage of a preferred embodiment of the present invention that the electronics components associated with an imaging sensor are not subjected to x-ray radiation as they are not directly in the path of the x-ray.
It is still another technical advantage of a preferred embodiment of the present invention to reduce the cost of digital x-ray imaging due to reduction in the number of cameras used.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.